Thickened aqueous slurry explosive composition containing ammonium nitrate trinitrotoluene surface active agent



United States Patent Oflice 3,508,981 Patented Apr. 28, 1970 US. Cl. 149-57 9 Claims ABSTRACT OF THE DISCLOSURE A slurry explosive composition containing 0.1 to 5.0%, by weight, of at least one surface active agent selected from the group consisting of an acid salt of a higher alkylamine, an alkyltrimethylam'rrronium chloride, an imidazoline derived from a fatty acid and aminoethyl ethanolamine, and a sodium salt of a higher alcohol sulfate. The slurry is stable in its properties and has higher explosion velocity.

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an explosive composition, particularly to a slurry explosive composition containing ammonium nitrate as a principal ingredient.

Description of the Prior Art Slurry explosives prepared by mixing ammonium nitrate, 2, 4, 6-trinitrotoluene (hereinafter referred to as TNT) and water are known as an effective industrial explosive, and have been used at sites such as hard rock or water springs, where ammonium nitrate-fuel oil explosives cannot be employed. Such slurry explosives are absolutely safe in handling, and can be very easily charged into a blasting hole. Therefore, in recent years, such slurry explosives have been charged by means of a forcing pump utilizing the slurry characteristics thereof. Such slurry explosives also have higher explosive velocity and are more excellent in explosive performance in comparison with the well known ammonium nitrate-fuel oil explosives. Additionally, such slurry explosives are lower in transportation cost and boring cost since such explosives are higher in density (in comparison with ammonium nitrate-fuel oil explosives).

With respect to the compounding ratio of ammonium nitrate and water, a concentrated solution of more than 65% by weight is generally used in the slurry explosive compositions. However, an ammonium nitrate solution in such high concentration necessarily coexists with crystals of ammonium nitrate at a temperature below its saturation temperature. This causes various problems in the preparation and use of a slurry explosive composition. For instance, because the crystals of ammonium nitrate tend to grow into macro plate form in a concentrated ammonium nitrate aqueous solution containing a thickening agent, such as carboxymethyl cellulose (hereinafter referred to as CMC), and gums, thereby its strength is considerably higher in comparison with crystals grown in the ammonium nitrate aqueous solution at the same concentration.

This is believed to be accounted for by the fact that in a concentrated aqueous solution of ammonium nitrate containing CMC or gums, the diffusion of ammonium nitrate in the solution is prevented because of the high viscosity thereof, and thereby all crystalline nuclei do not grow uniformly. These relationships are described at page 592 of the second volume of Applied Colloidal Chemistry by S. Oguri, published by Maruzen Publishing Co., 1959. Even in experiments by the present inventors, it was found that when 1.5% (based on the weight of water) of guargum was added to a concentrated aqueous solution of ammonium nitrate at a concentration of 68% (by weight) and the mixture was thoroughly stirred and allowed to stand under environmental conditions, an irregular plate form of the crystals approximately 10 x 10 x 2 mm. separated, and settled down on the beaker bottom within two days.

Considering the results obtained by the present inventors in a field blasting test, that is, a slurry explosive containing large separated plate crystals therein explodes completely in about one-third of the total thereof, but a slurry explosive containing no crystals explodes completely, it can be seen that the enormous growth of crystals clearly badly effects the power of an explosive.

The thickening agent described above, such as CMC, gums, dextrine, nitrocellulose, pectin, gelatin, acrylamide, etc., is employed in order to give sufficient flowability for easy handling. Moreover, during long period storages in a powder magazine, it is expected to maintain the physical properties of the explosive, namely viscosity, uniform composition and fiowability, close to those encountered at manufacture. However, when employing such explosives in a cold district, there are many unfavorable problems, such as flowability eliminated due to crystallization of ammonium nitrate during storage, and an enormous crystal as described above is separated and settled down due to the difference of the specific gravity between the solid and the liquid. This promotes sedimentation of co existing TNT, and thereby the explosives cannot easily be filled into a hole, and, even though filling can be done, the explosives cannot be completely detonated because of the non-uniformity of the composition thereof.

Particularly, such a slurry composition cannot be charged by pumping and lfilling up apparatus, and therefore, operation efliciency is lowered. To prevent the problems mentioned above, a treatment for heating the composition at a temperature a little above its saturation temperature is generally adopted. The maintenance of constant temperature is particularly important during cold usage. However, the maintenance of constant temperature is expensive and sometimes is diflicult with respect to the safety thereof. Therefore, this is not a satisfactory method.

As an alternative, cross-linking agents can be added to gelate the solution so that all suspended materials are dispersed with a constant distance. However, the solution, when physically geleted, loses its fiowability and therefore cannot be easily filled into a blasting hole. For example, in case of using a certain cross-linking agent in combination with acrylamide or calcium lignin sulfonate, it is extremely difiicult to fill the explosive into a hole since these agents give a high gel strength to the explosive.

The present inventors have found a method of solving such problems by adding certain additives to slurry explosives, and also have surprisingly found that the slurry explosive compositions so stabilized have an increased explosion velocity.

Thus, the first object of the present invention is to provide a slurry explosive composition which does not separate into an enormous crystal, and which is stable under severe storage conditions.

A second object of the present invention is to provide a slurry explosive composition having a high explosion velocity.

SUMMARY 01 THE INVENTION The slurry explosive of the present invention is prepared by mixing a composition containing 40 to of ammonium nitrate, 5 to 20% of water, 5 to 55% of TNT, and 0.1% to 5% of one or more thickening agents such as CMC, locust bean gum and guargum, with at least one agent selected from the group consisting of an acid salt of a higher alkylamine, an alkyltrimethylammonium chloride, and imidazoline derived from a fatty acid and aminoethyl ethanolamine and a sodium salt of a higher alcohol sulfate in an amount of greater than 0.1%, based on the weight of the composition. In the present invention, all percentages are by weight.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS A slurry explosive containing such surface active agents maintains a remarkable stability over a long period of time. For example, the results of stability tests are shown in following Table 1. A slurry explosive (A) was prepared by adding 0.20 part of CMC, 0.20 part of locust bean gum and 0.07 part of guargum to 44.8 parts of ammonium nitrate containing 1.1 wt. percent of octadecylamine, acetate and, after stirring the mixture, adding 19.9 parts of Water and 34.83 parts of TNT (greater than 60% thereof having a particle size greater than 30 mesh sieve: Japan Industrial Standard). A slurry explosive (B) was prepared by adding the same amount of octadecylamine acetate as in slurry explosive (A) during the final step of the slurry explosive preparation process. A slurry explosive (C) was prepared in the same manner as in the preparation of slurry explosive (A) except that ctadecylamine acetate was not added. The stability of the slurry explosive was examined by the following method.

The slurry explosives were filled to a height of 20 cm. into mesh cylinders having an inner diameter of 4 cm., and allowed to stand while undergoing a temperature change between 2 C. and 50 C. once a day.

The stable period represents the day at which crystals of ammonium nitrate and TNT separated from the suspension and a liquid layer appeared, that is the day at which the composition can be recognized to be nonuniform by observation.

Table 1 Explosive Stable period (days) (A) 44 (B) 48 (C) 17 TABLE 2 Filling Explosion Density Velocity Explosive (g./cm. (m./sec.)

The values of the explosion velocity and the filling density are shown as the average value of three measurements.

As is obvious from the experimental'results shown in Tables 1 and 2, the performances of the slurry explosive compositions of the present invention are not significantly varied 'by' the order of mixing the specific surface active agent therein. An acid salt of an higher alkylamine, an alkyltrimethylammonium chloride, an imidazoline derived from a fatty acid and aminoethyl ethanolamine and a sodium salt of a higher alcohol sulfate are preferably used in an amount of within 0.1 to 5.0% based on the weight of the composition usually comprising ammonium nitrate, water, TNT and a thickening agent, etc. If the amount is smaller than this range, a suflicient effect is not obtained in the stability and explosion velocity. If the amount is larger than this range, the stability is not as increased, and therefore use of a large amount is not preferable from an economical point of view and is not preferable from the viewpoint of quality and performance of the slurry explosive composition.

The exact compounding proportion of the components constituting the slurry explosive composition and the compounding order of the components are not significantly varied from those conventionlly used in the art, and not to be limited thereby since similar state of the art proportions and methods may be used.

In the present invention, the acid salt of a higher alkylamine includes nitrates and acetates of an alkylamine having 14 to 18 carbon atoms, the alkyl of the alkyltrimethylammonium chloride has 12 to 18 carbon atoms, a fatty acid for use in the production of the imidazoline has 12 to 18 carbon atoms and an alcohol of the sodium salt of higher alcohol sulfate has 8 to 18 carbon atoms.

The present invention will be further illustrated by the following examples, however, it is not limited by these examples. The parts and percentages in the examples are shown by weight, unless specifically indicated.

Example 1 44.53 parts of powdered ammonium nitrate containing 0.5 parts of various surface active agents had, respectively, added thereto 0.2 part of CMC, 0.2 part of locust bean gum, and 0.70 part of guargum. The mixtures were sufficiently stirred, and 20 parts of water and 35 parts of TNT (greater than 60% thereof having a particle size greater than 30 mesh sieve) were added thereo to obtain the respective slurry explosive compositions. The slurry explosives prepared were, respectively, filled to a height of 20 cm. into mesh cylinders having an inner diameter of 4 cm. and allowed to stand while making a temperature change between 2 C. and 50 C. once per day. The stable period is represented by the number of days at which separation of the slurry layer and the liquid layer was observed. The results are shown in Table 3.

TABLE 3 Stable Period Width and Length Surface Active Agent (day) Crystal Form of Crystal Present Invention:

Octadecylamine 44 Flat needle Below 10 mm. x below acetate. 1.0 mm.

Lauryltrirnethyl- 47 ..do Below 10 mm. x 1-3 ammonium mm. chloride.

Octadecyl- 42 Needle Below 10 mm. x trlmethylbelow 1.0 mm. ammonium chloride.

Imidazoline 50 Extremely fine Do.

derived from fibrous. stearic acid and aminoethyl ethanolamine.

Sodium salt of a 44 do Do.

higher alcohol sull'ate.*

Reference:

Laurylarnine 20 do Do.

acetate.

Polyoxyethylene 17 Flat needle Below 10 mm. it above laurate. mm.

Dodecylbenzone 17 Extremely fine Below 10 mm. 1: sodium fibrous. below 1.0 mm. sulfonate.

Acid fuchsine 21 Fibrous 10-30 mm. x below None 20 Flat needle Below 10 mm. x

below 3 mm.

*Monogen S: Trademark of the surface active agent prepared by Daiiehi Seryaku 00., in Japan.

In this experiment a repetition of the appearance and elimination of crystals of ammonium nitrate was observed in the cylinder and, when an enormous crystal separated,

the separation of solid and liquid layers was observed at ten days and at periods in excess thereof.

Example 2 In a manner as in Example 1 (with the exception of a difference in the amount of surface active agent) slurry explosives were prepared. The explosion velocity of the explosives prepared was measured according to the Dautriche method using a No. 6 electric cap as the initiator and 10 g. of tetryl as the booster. The results are shown in Table 4.

TAB LE 4 Amount of surface active Filling Explosion agent density velocity Surface active agent percent (g./cm. (In/sec.)

Present invention:

. 0. 1 1. 34 5, 620 Octadecylamine acetate O 5 1, 39 5, 400 1. 1. 36 5, 200 0. 1 1. 36 5, 590 Lauryltrimethylammonium 460 chloride 1.0 1.24 5, 3,00 0. 1 l. 31 5, 380 Octadccyltrlrnethyl-ammonium Q 5 1 34 5, 390 ch ride. 1.0 1. 37 5, 420 Inudazohne derived from stearic 0 1 1 34 5, 220 acid and amino-ethyl ethanol- 0, 5 1 3 5 3 0 amine. 1.0 1. 34 5, 410 0. 1 l. 41 5, 310 Sodium salt of higher alcohol sul- 5 1 5, 260 ia1e.* 1. 0 1. 5, 340 Reference:

0. 1 1. 39 4, 920 Laurylannne acetate 0, 5 1. 29 4, 840 l. 0 1. 33 4, 808 0. l 8 5 8 Polyoxyethylene laurate 5 g 51 800 1. 0 1. 30 5, 030 0. 1 1. 41 4, 190 Sodium dodecylhcnzene sulfo- 0.5 1. 43 5, 280 hate. 1. 0 1. 4, 730 0.1 1. 3s 5, 290 Acldw magrwm 0, 5 1, 40 5, 320 1. O l. 34 5, 330 None 1. 37 5, 061

*Monogen S: The Trademark of the surface active agent prepared by Daiichi Seiyaku 00., in Japan.

The values in the table are the average values of three measurements.

What is claimed is:

1. A slurry explosive comprising about 40 to about 75 ammonium nitrate,-about 5 to about 20% water, about 5 to about 55% trinitrotoluene and about 0.1 to about 5% of a member from the group consisting of carboxymethylcellulose, locus bean gum, guargum and mixtures thereof, and at least one agent selected from the group consisting of an acid salt of a higher alkylamine, an alkyltrimethylammonium chloride, an imiazoline derived from a fatty acid and aminoethyl ethanolamine, and a sodium salt of a higher alcohol sulfate, the amount of said agent being greater than about 0.1% based on the weight of said composition, said percentage being by weight.

2. A slurry explosive according to claim 1 wherein said agent is octadecylamine acetate.

3. A slurry explosive according to claim 1 wherein said agent is octadecyltimethylammonium chloride.

4. A slurry explosive according to claim 1 wherein the amount of the agent is about 0.1 to about 5%, based on the weight of the composition.

5. A slurry explosive according to claim 1 wherein said agent is selected from the group consisting of nitrates of an alkylamine having from 14-18 carbon atoms, acetates. of an alkylamine having 14-18 carbon atoms, an alkyltrimethylam-monium chloride wherein the alkyl group has 12-18 carbon atoms, an imidazoline derived 6 from a fatty acid and aminoethyl ethanolamine wherein the fatty acid has 12-18 carbon atoms, and a sodium salt of a higher alcohol sulfate wherein the alcohol has 8-18 carbon atoms.

6. A method for improving the stability and the explosion velocity of a slurry explosive which comprises mixing with a composition contain about 40 to about ammonium nitrate, about 5 to about 20% Water, about 5 to about 55% trinitrotoluene and about 0.1 to about 5% of a member from the group consisting of carboxyrnethylcellulose, locust bean gum, guargum and mixtures thereof, at least one agent selected from the group consisting of an acid salt of a higher alkylamine an alkyltrimethylammonium chloride, and an imidazoline derived from a fatty acid and aminoethyl ethanolamine, and a sodium salt of a higher alcohol sulfate, the amount of said agent being greater than about 0.1% based on the weight of said composition, all of said percentages being by weight.

7. A slurry explosive according to claim 6 wherein said agent is selected from the group consisting of nitrates of an alkylamine having from 14-18 carbon atoms, acetates of an alkylamine having 14-18 carbon atoms, an alkyltrimethylammonium chloride wherein the alkyl group has 12-18 carbon atoms, an imidazoline derived from a fatty acid and aminoethyl ethanolamine wherein the fatty acid has 12-18 carbon atoms, and a sodium salt of a higher alcohol sulfate wherein the alcohol has 8-18 carbon atoms.

8. A method for the production of a slurry explosive with improved stability and explosion velocity which comprises mixing with a composition containing about 40 to about 75% ammonium nitrate, about 5 to about 20% water, about 5 to about 55% trinitrotoluene and about 0.1 to about 5% of a member selected from the group consisting of carboxymethylcellulose, locust bean gum, guargum and mixtures thereof, at least one agent selected from the group consisting of an acid salt of a higher alkylamine, an alkyltrimethylammonium chloride, an imidazoline derived from a fatty acid and aminoethyl ethanolamine, and a sodium salt of a higher alcohol sulfate, the amount of said agent being greater than about 0.1% based on the weight of said composition, said percentages being by weight.

9. A slurry explosive according to claim 8 wherein said agent is selected from the group consisting of nitrates of an alkylamine having from 14-18 carbon atoms, acetates of an alkylamine having 14-18 carbon atoms, an alkyltrimethylammonium chloride wherein the alkyl group has 12-18 carbon atoms, an imidazoline derived from a fatty acid and aminoethyl ethanolamine wherein the fatty acid has 12-18 carbon atoms, and a sodium salt of a higher alcohol sulfate wherein the alcohol has 8-18 carbon atoms.

References Cited UNITED STATES PATENTS 2,930,685 3/1960 Cook et al l49-57 X 2,946,671 7/1960 Marti 149-57 X 2,946,672 7/1960 Marti l49-57 X CARL D. QUARFORTH, Primary Examiner S. J. LECHERT, Assistant Examiner US. Cl. X.R. 

